So today Lorien Cleaner Pro is offered... not commenting on the app itself, but rather an article referenced in the comments that's out of date as well as misleading. Lots of people make lots of money hosting ads on web sites if they generate enough traffic. It doesn't matter if whatever's on that site is true or not, accurate or not -- all that matters is will enough people click on the site to read it [traffic]. So tons of people write whatever, getting paid by the word, meaning the faster they can type something the more they earn. I guess that this is just a reminder of sorts that we all have to be our own fact checkers.
"Worth reading this before downloading.
https://www.howtogeek.com/162683/pc-cleaning-apps-are-a-scam-heres-why-and-how-to-speed-up-your-pc/".
FWIW, article is not 100% accurate. The main gist of the article: "PC cleaning apps are digital snake oil." & "To investigate, we ran MyCleanPC...", is Partly true, using as example one of the more questionable apps out there. A few of the article's claims...
"Windows can remove junk files, clear Internet browsing traces, and defragment your hard drive without installing additional software."
These 3 claims are true, but not mentioned is how well Win10 does the job. To get rid of junk there's Disk Cleanup, which is being deprecated in favor of the options in Settings -> System -> Storage. Run it & afterwards check the 2 temp folders, where you'll find plenty to delete. Disk Cleanup can get rid of no longer needed Windows Update files, But, run it on 2 identical copies of Win10 on the same PC, and you'll get different results -- different amounts of space reclaimed (!)(?). Trying to remove the same junk via Settings OTOH *may* work, but usually does not, and again will not empty the 2 temp folders, which are the most obvious place to start.
[Note: *usually* junk in the temp folders doesn't matter, as long as you're not running out of disk space, but it makes backup images larger, and occasionally can cause problems, e.g. when registry entries improperly reference files in those 2 folders.]
2nd, the new Chromium-based Edge can be set to delete temp files when it's closed, and those temp files can also be [allegedly] deleted using Disk Cleanup. Depending on what sites you visit, & how many, Edge's cache can grow too large, causing Edge, & often Win10 to lock up, despite closing the browser &/or running Disk Cleanup -- removing that junk has to be done manually so Edge will work properly again. And of course Win10 does nothing about the junk accumulated by the browsers people actually use, e.g. Chrome, Firefox, & Opera.
3rd, disk defragmentation is more complicated than the article might suggest. Third Party defrag apps will use Windows' API, but they usually go a step further, moving files you use most to the fastest part of the drive platter.
The HTG article goes on to say: "Registry entries are generally not a problem — there’s a reason Microsoft once created a registry cleaner of their own before discontinuing it and advising people not to use registry cleaners."
The first part is *usually* true, though there are all sorts of exceptions -- just like there are shoddy, incompetent mechanics, doctors, contractors etc., idiots sometimes write software. With Windows registry, there are No enforced rules -- coders can do whatever they want. [UWP might have put an end to that, but UWP as a platform failed.] Registry size used to be a problem, but with Win10 being essentially reinstalled once or twice a year, not so much any longer. At the same time however, Windows devices may use lower end CPUs, along with less RAM & storage than ever before, so tolerance for an overlarge registry may be reduced.
As for the 2nd part, Google doesn't seem to corroborate that statement.
Otherwise, the article, from 2016, is simply out of date. "Run the Disk Defragmenter included with Windows. This isn’t necessary if you use a solid-state drive." is No Longer True. Win10 will By Design defrag SSDs about once a month -- Microsoft Engineers found it necessary -- so leave drive optimization set to auto.
The Disk Cleanup test referenced was performed in 2011, LONG before Win10 20H1. It doesn't take much time or any skill to check the 2 temp folders afterward. And again, Disk Cleanup is being deprecated.
The article says: "If you regularly see errors on your computer: Run an antivirus program and an antimalware program to scan your computer for malware-producing error messages. Google error messages you see regularly to find fixes for them."
There are apps that will scan the disk with Windows not running, which may pick up malware, but Do Not assume that when a normal AV scan doesn't find anything that everything's cool. Malware's Much better than that nowadays. And while you can certainly Google for error messages, Don't Hold Your Breath. Sadly Win10 is chock full of generic error hexes that can be caused by so many things they're utterly worthless.
Finally, realize that the Refresh Your PC option recommended is hit or miss. Restore an Image backup, or try the DISM repair options, or if WIn10 will run, mount a setup ISO, then run setup to reinstall Win10 preserving your software etc.